This proposal outlines a new physical approach for myothermal measurements based upon the thermal-optical behavior of various cholesteric liquid crystals which represent the ultimate in temperature detection. By measuring the intensity of selectivity reflected light at constant wavelength, accurate heat quantities can be accessed, down to the level of "temperature noise" in the system. Year I goals include the completion of a prototype system evaluating system parameters, and calibration of the thermal response in terms of sensitivity and temporal resolution. Year II goals include the detailed comparison of frog sartorii isometric heat production measurements with those previously reported in the literature; special interest will be given to an analysis of the earliest heat production rates; additional shortening heat experiments are also planned. Year III, utilizing microencapsulated liquid crystals in conjunction with single, large myofibers of Balanus sp., is to be devoted to direct, intracellular heat production studies on isometric preparations. Future work using liquid crystal thermography appears limitless and generally applicable to many cellular thermal measurement problems.